How to fix flash player in firefox?

Question

Adobe Flash

Help with a problem!
After a recent Windows 10 update, a flash error in Firefox when going into full screen mode. The image is divided into two halves: the left half is normal, the right half is somehow shifted and does not react to anything (this is how it can be described closest to the truth). And this is with hardware acceleration disabled, and with hardware acceleration enabled, there is another problem (and now not in full-screen mode either): the image update freezes or slows down. That is, the speed of work is normal, but the image itself seems to freeze for a while and is not updated. I tried to completely rearrange the flash - nothing helped. Specially put a clean firefox-portable - the same symptoms. Moreover (!) in Chrome, the flash works fine, nothing slows down and the full-screen mode is displayed correctly.
Until yesterday, everything was ok - tell me, maybe tweak something in the settings, the problem is only in Firefox, apparently ...